1. Field of the Invention
The present invention relates to a light emitting element such as a an organic electroluminescent element. Particularly, the present invention relates to a light emitting element that has high luminance and luminous efficiency, and also has superior endurance.
2. Description of the Related Art
In recent years, organic electroluminescent (EL) elements have been actively investigated and developed, since these elements can emit light with high luminance through a low-voltage driving process. In general, an organic EL element is constituted by a light emitting layer and a pair of opposing electrodes that sandwich this layer, and electrons, injected through a cathode, and holes, injected through an anode, are recombined in the light emitting layer so that excitons are generated, and utilized to emit light.
Recently, organic EL elements have become highly efficient. The external quantum efficiency of an organic EL element using an iridium complex as a light emitting material has exceeded 5%, which had been conventionally considered as a limit, and reached 8% (Applied Physics Letters, Vol. 75, page 4, published in 1999).
Japanese Patent Application Laid-Open (JP-A) No. 2001-247498 discloses an organic EL element using a material consisting of carbon and fluorine.
However, the conventional organic EL elements fail to provide sufficient endurance, and there is strong demand for development of organic EL elements having high luminance, high luminous efficiency, and superior endurance.